School districts may purchase out of contingent funds school textbooks or electronic textbooks, instructional materials, and the technological equipment necessary to gain access to and use electronic textbooks from the publishers and manufacturers at the prices listed on the sworn statement published on the retail dealer’s website and may designate a retail dealer or dealers to act as the agent of the district in selling them to pupils. Such dealers shall at stated times make settlement with the district for books sold. Such dealers shall not sell textbooks at prices which exceed a 10% advance on the net prices as listed on the sworn statement.